"Of course," Sanchez replied, when asked at the World Economic Forum in Davos, Switzerland, if the two nations would send delegations to the June 28-30 gathering.

"They are big democracies, very well established and consolidated democracies, and I think it is also very important for NATO and the European Union to have them on board as NATO allies," he added.

Spain will speed up its parliamentary procedure to give its backing for the entry of the two nations in the alliance, the prime minister said.

Sweden and Finland applied to join the transatlantic alliance in the wake of Russia's invasion of Ukraine on February 24.

But all 30 of NATO's members must approve the enlargement, and Turkey has warned it will not support their applications as things stand.

Ankara has long accused Nordic countries -- in particular Sweden, which has a strong Turkish immigrant community -- of harbouring outlawed Kurdish militants as well as supporters of Fethullah Gulen, the US-based preacher it accuses of being behind a failed 2016 coup.

Sweden and Finland will send delegations to Ankara this week hoping to resolve the matter, Finnish Foreign Minister Pekka Haavisto said earlier Tuesday.

The two countries' bids to join NATO constitutes one of the most significant changes in Europe's security architecture in decades, not least because Finland shares a 1,300-kilometre (800-mile) border with Russia.